1. Field of the Invention
The present invention relates generally to an electromagnetic valve apparatus. More particularly, the present invention is concerned with an improved structure to remove foreign matter and to establish quick response for an electromagnetic valve apparatus.
2. Description of the Related Art
An electromagnetic valve is often used in, for example, a hydraulic control circuit for controlling a hydraulic flow. A conventional electromagnetic valve is disclosed in FIG. 2. Referring now to the FIG. 2, the electromagnetic valve basically includes a main body 50, a holder 51, a coil 52, a core 53 and a spool valve 54. The spool valve 54 is comprised of a spool 54a and a spool cylinder 54b. A spring 55 is arranged between the spool 54a and the core 53. A spring adjuster 56 is connected with the core 53 via a threaded portion 56a. The set tension of the spring 55 can be varied by turning the spring adjuster 56.
A cylindrical body 57 is fixed to the main body 50. The core 53 is connected to the cylindrical body 57, and the core 53 is fixed to the main body 50. The coil 52 is arranged on the outer surface of the cylindrical body 57 via a coil bobbin 52a. The core 53, the spring adjuster 56, the spring 55, the cylindrical body 57, the coil bobbin 52a and the coil 52 are accommodated in the holder 51. The main body 50 is tightly fitted with the holder 51 and cylindrical body 57. The main body 50 has a cylindrical portion 50a. An inlet port 58 and an outlet port 59 are forming in the cylindrical portion 50a of the main body 50. The spool cylinder 54b is slidably arranged at the inner portion of the cylindrical portion 50a. A hole 60 is formed on the surface of the spool cylinder 54b. The spool valve 54 is slidably connected with the inner portion of the cylindrical portion 50a of the main body 50. The spool 54a and the spool cylinder 54b are tightly connected to each other.
In operation, an electrical signal is applied to the coil 52. This energizes the electromagnetic valve and moves the spool valve 54 to the open position, which is to the right in FIG. 2. As a result, the inlet port 58 and the outlet port 59 communicate with the drain port 61. When the electrical signal is removed, the coil 52 is deenergized, and the spring 55 operates to close the valve by moving the spool valve to the left direction in FIG. 2.
However, there are problems with the above-described design. For example, foreign matter may enter into the spool valve 54 and jam it into either the open or closed position. Even if the valve is not jammed, its operation may be slowed by such foreign matter.